Re: [Haskell-cafe] Class/Instance : what am I doing wrong in this example ?

On Dec 20, 2007 5:36 PM, Jules Bean wrote:

2. Maybe you want lots of possible different "a"s for each "g". Then you make "a" a parameter of the class too.

3. Maybe you want just one particular "a" for each "g". I.e. "g" determines "a". Then you can proceed as for (2), but add the functional dependency | g -> a

Practically, what would be the difference between 2. and 3. ? David.